1. Field of the Invention
This invention is concerned with preparation of control programs for numerically controlled machine tools.
2. Brief Description of the Prior Art
Numerically controlled machine tools have enjoyed great success in recent years, particularly for the production in moderate volume of precision parts such as are common in the aerospace industries since both the cost and accuracy of the finished product are considerably improved over conventional machining methods in which highly skilled machinists manually set up and carry out the machining processes. In these machines the control of the machine tool movements with respect to the workpiece is accomplished by means of an automated control program which may also control automatic tool changing mechanisms and sequencing thereof so that workpieces may be automatically machined.
A rather substantial practical difficulty is encountered by users of such equipment however in creating the control programs which are necessary for machining of a given part and this is particularly exacerbated in the case of small to medium volume usage of such equipment. This difficulty arises from the nature of programming methods which have been utilized in the past, i.e., an experienced programmer who himself must decide the machining methods and sequences to be utilized in carrying out the process, must, from a mere inspection of the part drawings, conceptualize in his mind the entire sequence of events, which sequence can involve an enormous number of individual control commands to the machine tool. This is so even to carry out relatively simple machining steps such as the position of the cutting tool during indexing, the extent of rapid traverse movement, the initiation of a slow in-feed, the in-feed rate, the spindle rotation rate, etc. Great care must be exercised since it is usually critical that the relative position of the workpiece and the cutting tools be calculated to prevent interference damage, such as broken tools, etc. caused by errors in properly positioning the various parts.
Thus, the mental effort required to carry out the composing of an entire program listing can be nightmarish and painstaking to the point where mistakes are impossible to avoid and a great deal of time is consumed in such program preparation. As noted, this problem is further exacerbated in the situation of the small to medium user of such equipment due to the almost absolute necessity of using an experienced machinist or at least one who is fully informed as to the methods of carrying out the machining processes. That is, small businesses seldom would have the volume of programming work necessary to justify the use of the services of a full-time programmer, yet on the other hand, can ill afford the loss even for a few days of their skilled machinists for this purpose. Other disadvantages are that such employees seldom are satisfied with such dual capacity duties, generally considering themselves either machinists or programmers, not both, thus creating employee relations problems.
Furthermore, the commingling of machinists and programmer skills renders the basic programming task akin to alchemy poorly understood by others within the business organization, including the business managers. This difficulty in understanding the process leads to both undue dependence on the individual charged with execution of this task, but also creates a certain reluctance in the minds of managers who would otherwise seize on the benefits of this equipment but hesitate to do so due to their lack of understanding.
It is, therefore, an object of the present invention to provide a method of preparing such program tapes and an aid for use in such preparation which reduces the required level of conceptualization of the actual process by the programmer.
It is a further object of the present invention to provide a method and aid for such preparation of control programs which greatly reduces the need for calculation of the relative position of the workpiece and cutting tool in preparing a program listing.
It is yet another object of the present invention to provide such method and aid which greatly simplifies the preparation of the program listing by the programmer and allows the programmer relatively unknowledgeable in machining processes to obtain information from a skilled machinist which can be easily used by programmer to carry out the preparation of the program listing.